Wound treatment

ABSTRACT

Use of a moulding composition comprising a polymer and a setting agent for wound debridement, wherein said use comprises adding water to said moulding composition to form a moulding fluid, applying said moulding fluid to a surface of a wound, allowing said moulding fluid to set in contact with said surface to form a solid covering on said surface, followed by removing said solid covering from the wound. The alginate composition adheres strongly to bacterial biofilms on the wound, whereby the biofilms are removed with the alginate composition. The moulding composition may be used in conjunction with a staining agent that undergoes a colour change in the presence of bacteria or bacterial polysaccharides to show the presence and removal of the biofilm. Also provided are methods of treating wounds using the compositions.

The present invention relates to wound treatment, in particular thedetection and removal of biofilm, and wound debridement.

When the skin is broken and a wound is produced, the normal woundhealing process begins. In healthy individuals there are essentiallythree phases of wound healing—the inflammatory phase, proliferationphase and the remodelling phase. The inflammatory phase begins at thetime of injury and usually lasts for four to six days. The wound iscleansed of bacteria and debris, and is prepared for healing. During theproliferation stage the wound contracts and granulation tissue is formedto fill in the defect. In an acute wound with no factors to impair thehealing, two to three weeks is all that is necessary to close even largewounds. In the final remodelling phase, the wound healing processcontinues, and the tissue ideally returns to its original strength. Thisphase may last from twenty one days to two years.

Wound healing becomes less straightforward in individuals who haveassociated medical problems. In some cases wounds cease to heal andbecome “chronic wounds” which remain in the inflammatory stage.

Wound bacterial biofilms can contribute to the development ofnon-healing wounds. It is well known that bacteria naturally formbiofilms when they are able to associate with an open wound. Non-healingwounds are often associated with individuals with impaired inflammatoryresponse, so bacteria can persist within a wound and establish a biofilmcommunity with cannot be overcome by the individual's natural defencesalone.

Biofilm removal from wounds is usually carried out via debridement.Debridement is the removal of necrotic, damaged or infected tissue fromand around a wound to expose healthy tissue. There are number ofdebridement techniques, the quickest and most selective of which issurgical debridement, in which a scalpel, scissors, or other instrument(including a laser) is used to cut necrotic tissue from a wound.However, during surgical debridement, underlying tendons, blood vesselsand other structures may be damaged. Surface bacteria may also beintroduced deeper into the body. Less invasive debridement methods maybe used; for example mechanical debridement, in which a saline-moisteneddressing is allowed to dry and adhere to the dead tissue. When thedressing is removed, the dead tissue is also removed. However, themethod is non-selective and may traumatise healthy or healing tissue,causing the patient severe pain.

Anti-biofilm agents may also be used to reduce the presence of biofilm.Anti-biofilm agents have been used in a number of industries such aswater treatment, food processing, beef processing, dairy and dentistry.One such agent is bovine lactoferrin. Pseudomonas in the presence ofbovine lactoferrin will divide normally but is unable to attach, andtherefore unable to form biofilm structures. Bovine lactoferrin is usedin the beef industry on the carcasses of meat to prevent biofilmformation.

An associated problem is the detection of biofilm at first instance.Even if there is no evidence of clinical infection, it is likely thatbiofilm bacteria play a large role in preventing the normal healingprocess from occurring. The nature of biofilm means that, unlikeplanktonic bacteria, it has a number of pathways to down-regulate itsvirulence, so that does not significantly damage the host. Due to thismodulation of risk factors, clinical signs of infection are often notobvious.

Accordingly, it is an object of the present invention to provide animproved method of treatment of wounds. In particular, the presentinvention is directed to improved compositions, kits and methods fortreatment of bacterial biofilms in wounds. The present invention is alsodirected to improved compositions, kits and methods for debridement ofwounds.

Alginate impression materials have been used for many years in dentistryto make impressions for prosthodontic, orthodontic or other appliances.Alginate casting materials are also widely used for craft and hobbypreparation of moulding casts. The present inventors have found that,surprisingly, alginate-containing compositions have a high affinity forbiofilm and necrotic tissue. Accordingly, alginate-containingcompositions may be of use in the treatment of wounds, in particular forwound debridement and biofilm removal.

The use of alginates, in particular alginate fibers, fabrics andhydrogels, as wound dressing materials is known. The alginate provides awound-friendly, hydrophilic, non-adherent and bioabsorbable woundcontacting surface to the dressing. The alginate dressings are left incontact with the wound for extended periods of at least several hours topromote wound healing. They are designed to be non-adherent to reducewound trauma when the dressing is removed. In particular, they form analginate hydrogel with wound fluid. The hydrogel has low physicalstrength and is non-adherent to the wound surface.

DE-A-102006029500 describes alginate compositions that harden to adimensionally stable alginate mass for application to wounds. Thecompositions contain an antimicrobial agent, and also contain awater-absorbing component such as a hydrocolloid to produce an absorbentwound dressing composition in situ on a wound.

WO-A-2007048193 describes wound dressing compositions that are solid,particulate mixtures of alginates in a low-water-activity antimicrobialmatrix such as honey.

WO-A-2005023176 describes hydrogel compositions for the delivery andsustained release of active agents to a wound. The hydrogel is formed insitu on the wound by gelling of an anionic polysaccharide with calciumions present in biological fluids. GB-A-1122796 and WO-A-2004080343describe applying an alginate hydrogel dressing onto wounds bysequentially applying a sodium alginate solution and a calcium chloridesolution to the wound.

EP-A-1666020 describes fluid alginate compositions containing a gellingagent that can be applied to a wound. The compositions set to form ahydrogel wound dressing in contact with the wound. The compositionsfurther contain foaming agents to generate carbon dioxide. EP-A-0380253describes another alginate composition that forms a foamed hydrogelfollowing application to a wound.

WO-A-9733632 describes fluid gel compositions that can be applied towounds containing a slow release gelling agent and an antimicrobialagent.

US-B-6174544 describes the use of an alginate gel for wound filling, incombination with a dressing containing calcium salts that leach into thegel to harden the gel so that the gel can be removed easily.

US-A-2007218285 describes alginate casting compositions for formingporous moulded articles. The moulded articles may be used for cosmeticpurposes, such as skin pads and face packs. The porous moulded articlesmay be used as wound dressings.

Newman et al. in Biomaterials, vol. 27 (7), pages 1129-1139 (2006)describes treating sodium carboxymethylcellulose hydrogel-forming fiberdressings with fluorescent dyes to visualise bacterial activity.

WO-A-2008072117 describes incorporating dyes into cyanoacrylate skinsealants. The dyes change colour in the presence of microorganisms toprovide an indication of infection.

WO-A-2010070292 describes compositions for application to skin orwounds, wherein the compositions contain colorants that are capable ofpreferentially staining biofilms.

WO-A-2006065349 describes elastomeric articles, such as surgical gloves,that contain a dye that changes colour in the presence ofmicroorganisms.

In a first aspect, the present invention provides the use of a mouldingcomposition comprising a polymer and a setting agent for wounddebridement, wherein said use comprises adding water to said mouldingcomposition to form a moulding fluid, applying said moulding fluid to asurface of a wound, allowing said moulding fluid to set in contact withsaid surface to form a solid covering on said surface, followed byremoving the solid covering from the wound.

Certain polymers and salts thereof are water soluble, but when combinedwith a setting agent and water, form a moulding fluid, which will set intime, to form a moulded solid on the surface with which it is incontact. In accordance with the present invention, the moulding fluid isallowed to set in contact with the surface of a wound. The set mouldingcomposition adheres only weakly to the skin and wound surface. When thesolidified moulding material is then removed from the wound, biofilm isalso removed. The term “wound debridement” herein refers to such removalof bacterial biofilms from the wound. Necrotic tissue, when present, isalso removed from the wound.

Suitably, the polymer and the setting agent are in the form ofparticulate solids, such as powders. The powders may be providedseparately or in admixture prior to use. In any event, water is added tothe components with mixing to form a moulding fluid. Suitably, themoulding composition and water are vigorously mixed until a pourable orspreadable consistency is reached.

Once the moulding fluid has set, the resulting moulded solid may be lefton the surface of the wound for a period of time. Alternatively, oncethe moulding fluid has set in contact with the surface of the wound, itmay then be removed immediately from the surface of the wound. Suitably,the setting time of the moulding fluid is sufficient that the mouldingcomposition may be applied to the wound surface, without undue haste.Suitably, the moulded solid is removed from the wound from about 2minutes to about 6 hours after application, typically from about 5minutes to about 1 hour after application, for example within 30 minutesof application.

More than one application and subsequent removal of the moulding fluidmay be carried out, depending on the bacterial biofilm population.

Suitably, the polymer comprises or consists essentially of one or morepolysaccharides. The polysaccharide may suitably be a polyanionicpolysaccharide. Suitably, the anionic polysaccharide is apolycarboxylate. Suitable polysaccharides include alginates, agar, guargum, hyaluronates, pectins, carrageenans, xanthan gums, sulfatedextrans, cellulose derivatives such as carboxymethyl celluloses, andoxidized celluloses. Especially suitable anionic polysaccharides arewater soluble alginates such as sodium alginate. It is thought that thepolysaccharide moulding materials have high affinity forglycopolysaccharides and mucopolysaccharides of the biofilm, and thatthis accounts for the good adhesion of biofilms to the polysaccharidepolymers.

Water soluble alginate salts include sodium alginate, potassiumalginate, and ammonium alginate. Most suitably, the alginate comprisesor consists essentially of sodium alginate.

The polymer may initially be dry mixed with a suitable setting agent toform a composition such that, when the composition is mixed with water,a fluid (pourable or spreadable) moulding composition is obtained.Suitably, the moulding fluid is a spreadable, viscous or thixotropicmaterial, for example it may have a viscosity of from about 1 Pa s toabout 300 Pa s, for example from about 10 Pa s to about 100 Pa s. It istherefore considerably more fluid than, for example, alginate dentalimpression materials. Suitably, the amount of water added to themoulding composition to form the moulding fluid is in a solids:waterratio by weight of about 1:1 to about 3:1. The water content of themoulding composition after it has solidified is therefore suitably fromabout 25 wt. % to about 50 wt. %. The moulding composition does notabsorb significant amount of water in contact with wound fluid, and isnon-porous. It therefore differs from the hydrogel-forming alginatewound dressings known in the art, which have high equilibrium watercontents and low tensile strength. Suitably, the set mouldingcomposition has an equilibrium water content less than about 50%.

The setting agent for polyanionic polymers may be a divalent (or higher)metal salt. Suitably, the setting agent is a divalent metal salt.Preferably, the setting agent is a calcium salt, suitably a sparinglysoluble calcium salt such as calcium sulphate or calcium silicate.Additional salts may be present, in particular antimicrobial salts suchas silver salts or zinc salts, or adjusting salts such as phosphates,silicates or carbonates of sodium, calcium or the like. The compositionsmay comprise a retarder such as trisodium phosphate, which reactsprimarily with the calcium salt to retard release of the calcium.

In other embodiments, the polymer may be a guar gum and the settingagent may be a borate salt, such as sodium tetraborate. In yet otherembodiments, the polymer may be a water soluble xanthan gum and thesetting agent may be a water soluble galactomannan gum, as described inEP-A-0792653.

Suitably, the moulding compositions of the present invention comprisefrom about 10 wt. % to about 40 wt. % of the polymer, for example fromabout 12 wt. % to about 30 wt. % of the polymer. Suitably, the mouldingcompositions of the present invention comprise from about 10 wt. % toabout 50 wt. % of the setting agent, for example from about 12 wt. % toabout 40 wt. % of the setting agent. All of these percentages are dryweight basis of the moulding composition.

Setting of the polymer suitably results in a coherent solid, plastic,elastic or gel-like mass. The mass suitably has sufficient tensilestrength be lifted from the wound in one piece. For example, the setcomposition may have a tensile strength of at least about 0.1 MPa,suitably at least about 0.3 MPa, more suitably at least about 0.5 MPa.The tensile strength is measured by casting a sheet of the compositionapproximately 2 mm thick in a flat mould, cutting a strip of dimensions5 cm×1 cm from the sheet, and measuring the tensile strength of thestrip in an Instron or similar apparatus. These tensile strengths areconsiderably higher than the tensile strength of the alginate hydrogelsthat have previously been used for wound treatment.

The moulding composition may be chromatic moulding composition, whichwill undergo a colour change when mixed with water to form a mouldingfluid and/or said composition is set (i.e. it is no longer a pourable orspreadable fluid). Suitable indicators include thymolphthalein andphenolphthalein, or mixtures thereof. These indicators turn a sodiumalginate/calcium sulphate moulding composition from white to pink whenwater is added to form the moulding fluid, then back to white when thecomposition has set.

It is envisaged that the moulding composition could be mixed with waterto form a moulding fluid. This mixing could be carried out in thevicinity of the patient, as no specialist equipment is required. Themoulding fluid could then be spread onto/poured onto and around thewound area and allowed to set (i.e. until the composition is no longerfluid). Advantageously, the moulding composition can cover an area ofany required size. Conventional wound dressings are manufactured invarious different sizes, and the most appropriate size must be selected.Using the moulding fluid of the present invention, a wound treatment ofpotentially any size or shape is provided.

Furthermore, conventional wound dressings may not make contact with thewound surface without the application of pressure, potentially causingthe patient discomfort. The nature of the moulding fluid used in thepresent invention allows an exact impression of the wound surface to bemade—in effect providing a custom made wound treatment.

Wounds located on joints or protrusions (such as the ankle) may bedifficult to treat using conventional wound dressings, due to theirnon-uniform shape. The moulding fluid used in the present invention maybe easily poured onto the area, before being allowed to set.

Suitably, the moulding composition used in the present invention issterile. This could be achieved by autoclaving, treatment with ethyleneoxide, dry heat sterilisation or gamma irradiation. The sterilizationwould suitably be performed on the dry polymer and setting agent, forexample packaged, either separately in admixture. Addition of sterilewater would then result in a sterile moulding composition forapplication to the wound.

The moulding composition of the present invention may comprise furtherelements. The moulding composition may comprise a filler. Suitablefillers include diatomaceous earth, anhydrous silicate, talc, calciumcarbonate, pearlite, silica, cellulose and aluminium hydroxide. Thefiller is suitably admixed with the polymer and optionally also with thesetting agent prior to use. For example, the invention contemplates drymixtures of filler, polymer and setting agent, preferably sterile andpackaged. Suitably, the moulding compositions of the present inventioncomprise from about 10 wt. % to about 80 wt. % of one or more inertfillers, for example from about 40 wt. % to about 70 wt. % of one ormore inert fillers on dry weight basis.

The compositions used in the invention may further comprise one or moreplasticisers. The optional plasticisers assist in providing a flexible,soft cured material in situ in the wound. Suitable plasticisers includemedically acceptable mineral oils, silicone oils, vegetable oils,stearates, hydrogenated ethers and esters, and mixtures thereof. Theplasticisers may be present, for example, in an amount of from about 1wt. % to about 20 wt. % of the composition on dry weight basis.

The compositions used in the invention may further comprise one or morehumectants. The optional humectants assist in maintaining the desiredhydrophilic property of the composition. Suitable humectants includemedically acceptable polyhydric alcohols such as glycerol, sorbitol,soft paraffin, urea 25 creams, lanoline, sodium pyrrolidone carboxylate(PCANa), gamma linolenic acid (evening primrose oil) and soya oil, teatree oil, coconut oil (or any other nut oil), camomile, aloe vera,jojoba oil, cocoamide or mixtures thereof. The humectants may bepresent, for example, in an amount of from about 0.1 wt. % to about 10wt. % of the composition on dry weight basis.

The moulding composition of the present invention may further comprisean active pharmaceutical ingredient, such as a topical antimicrobialagent. Suitable topical antimicrobials include antibiotics such asBacitracin or Neosporin, chlorhexidine, Laurie arginate, metallicsilver, and silver compounds such as Silver sulfadiazine. Suitably, theactive pharmaceutical ingredient is present in an amount of from about0.001 wt. % to 5 wt. %, for example from about 0.1 wt. % to about 2 wt.% based on the dry weight of the composition.

In embodiments, the method further comprises applying to the wound astaining agent that undergoes a colour change in the presence ofbacteria or bacterial polysaccharides.

The water soluble polymer and the setting agent may be dry packagedtogether before use, for example as a kit with the staining agentpackaged separately from the water soluble polymer and the settingagent.

The staining agent will undergo a colour change in the presence ofbacteria or bacterial polysaccharide. Staining agents of this type aredescribed in WO-A-2010070292, WO-A-2006065349 and WO-A-2008072117. Asuitable staining agent is a copper phthalocyanine dye. An example of acopper phthalocyanine dye is Alcian blue, which is also known as Alcianblue 8GX, Ingrain blue 1, and C.I. 74240. Alcian blue specifically bindsto polysaccharides, staining them blue-green. As biofilm containspolysaccharide, Alcian blue can be used as stain to indicate thepresence of biofilm on a wound surface.

The use of a staining agent to indicate areas of significant biofilmwill allow areas of high bacterial burden to be directly treated bydebridement. This visual indication of biofilm burden will preventover-debridement and incorrect diagnosis. The removal of the colouredstaining agent onto the solidified alginate composition also givesvisual proof of the effectiveness of the debridement.

In a further aspect, the present invention provides a method of treatinga wound comprising the steps of: mixing a moulding compositioncomprising a polymer and a setting agent for said polymer with water toform a moulding fluid; applying said moulding fluid to a surface of awound, allowing said moulding fluid to set in contact with said surface,followed by removing said moulding composition from the wound. Suitably,the moulding composition is as described above in relation to the firstaspect of the invention. Suitably, the method further comprises applyinga staining as sescribed above to the wound prior to the application ofthe moulding fluid.

In embodiments, the wound may be a chronic wound such as a dermal ulcer.The uses and methods according to the present invention suitably do notcomprise application the composition to mucous membranes, teeth, orgums.

It will be appreciated that any feature or embodiment disclosed hereinin relation to any one embodiment of the invention may also beapplicable to any of the other embodiments. This applies in particularto the components and composition of the moulding composition.

All patent publications referred to herein are hereby expresslyincorporated in their entirety.

EXAMPLE 1 Use of Alcian Blue as a Biofilm Staining Agent

Pieces of raw chicken breast meat were studied as a model for biofilmand necrotic tissue formation. The first three pieces were inoculatedwith Pseudomonas aeruginosa before being left at 37° C. for 24-48 hr. Asolution of Alcian blue was then applied to the surface of the chicken.Areas of blue-green staining indicated the presence of bacterialbiofilm. As expected, the chicken pieces that were inoculated had ahigher bacterial biofilm population than non-inoculated piecescontaining the normal flora.

EXAMPLE 2 Formation and Application of the Moulding Fluid

Life Casting Alginate (obtained from Craftwise Ltd) was mixed vigorouslywith an equal volume of cold water. Once a porridge-like consistency wasobtained, the moulding fluid was applied to pieces of chicken, preparedaccording to Example 1. The composition was left for about 30 minutes toset completely, after which the resulting flexible mould material wasseparated from the chicken pieces. It was observed that the removal ofthe composition from the chicken pieces also removed large amounts ofbiofilm, as indicated by the blue-green staining on the inner surface ofthe removed moulding material. The procedure was repeated for a piece ofchicken which was subjected to two consecutive applications (followed byremovals) of the fluid forming composition. It was evident that thesecond cast also removed necrotic material, indicated by the presence ofthe blue-green stain on the inside of the cast and of the necrotic,yellow tissue itself.

1-14. (canceled)
 15. A kit comprising a moulding composition andinstructions for performing a method for treating a wound; wherein themoulding composition comprises a water soluble polymer and a settingagent, the polymer comprises at least one polyanionic polysaccharide,and the setting agent comprises a divalent metal salt; and wherein theinstructions comprise adding water to the moulding composition to form amoulding fluid, wherein the polymer and the setting agent are solids,and the moulding fluid comprises a solids to water ratio by weight ofbetween 1:1 and 3:1; applying the moulding fluid to a surface of thewound; allowing the moulding fluid to set in contact with the surface toform a solid covering; and removing the solid covering from the wound todebride the wound, wherein the removing is performed not more than sixhours after the applying.
 16. The kit of claim 15, wherein the kitfurther comprises a staining agent packaged separately from the watersoluble polymer and the setting agent, wherein the staining agent isadapted to undergo a colour change in the presence of bacteria orbacterial polysaccharides.
 17. The kit of claim 16, wherein the stainingagent comprises a copper phthalocyanine dye.
 18. The kit of claim 16,wherein the instructions further comprise applying to the wound thestaining agent prior to applying the moulding fluid.
 19. The kit ofclaim 15, wherein the water soluble polymer comprises at least on of analginates, an agar, a guar gum, a hyaluronate, a pectin, a carrageenan,a xanthan gum, a sulfate dextran, and a cellulose derivative.
 20. Thekit of claim 15, wherein the water soluble polymer comprises at leastone of sodium alginate, guar gum, and xantham gum.
 21. The kit of claim15, wherein the setting agent comprises at least one of a calcium salt,a borate salt, and a water soluble galactomannan gum.
 22. The kit ofclaim 15, wherein the moulding composition further comprises anantimicrobial salt.
 23. The kit of claim 22, wherein the antimicrobialsalt comprises at least one of a silver salt and a zinc salt.
 24. Thekit of claim 15, wherein the setting agent comprises a calcium salt. 25.The kit of claim 24, wherein the calcium salt comprises at least one ofcalcium sulphate and calcium silicate.
 26. The kit of claim 24, whereinthe moulding composition further comprises a retarder adapted to reactwith said calcium salt to retard the release of calcium.
 27. The kit ofclaim 26, wherein the retarder comprises trisodium phosphate.
 28. Thekit of claim 15, wherein the moulding composition further comprises afiller in an amount of from about 10% to about 70% dry weight basis. 29.The kit of claim 15, wherein the water soluble polymer and the settingagent are in the form of particulate solids in admixture.
 30. The kit ofclaim 15, wherein the moulding composition comprises from about 12% toabout 30% dry weight basis of the polymer and from about 12% to about40% dry weight basis of the setting agent.
 31. A kit comprising amoulding composition and instructions for performing a method fortreating a wound; wherein the moulding composition comprises a watersoluble polymer and a setting agent, the polymer comprises at least onesodium alginate, guar gum, and xantham gum, and the setting agentcomprises at least one of a calcium salt, a borate salt, and a watersoluble galactomannan gum; and wherein the instructions comprise addingwater to the moulding composition to form a moulding fluid, wherein thepolymer and the setting agent are solids, and the moulding fluidcomprises a solids to water ratio by weight of between 1:1 and 3:1;applying the moulding fluid to a surface of the wound; allowing themoulding fluid to set in contact with the surface to form a solidcovering; and removing the solid covering from the wound to debride thewound, wherein the removing is performed not more than six hours afterthe applying.
 32. The kit of claim 31, wherein the water soluble polymercomprises sodium alginate and the setting agent comprises calciumsulphate.
 33. The kit of claim 32, wherein the moulding compositionfurther comprises a retarder adapted to react with said calcium salt toretard the release of calcium.
 34. The kit of claim 33, wherein theretarder comprises trisodium phosphate.
 35. The kit of claim 31, whereinthe kit further comprises a staining agent packaged separately from thewater soluble polymer and the setting agent, wherein the staining agentis adapted to undergo a colour change in the presence of bacteria orbacterial polysaccharides.